Generally, in image reading apparatuses provided in image forming apparatuses such as a copier, fax machine or digital multi-functional peripheral, or image reading apparatuses contacted to a computer via communication means such as a network, light reflected from a document serving as the illumination target that is illuminated by an illuminating device including a light source for illuminating the document is read as the document image.
For example, a conventional image reading apparatus includes a light source unit in which an illuminating device including a light source portion (for example, a bar-shaped light source such as a halogen lamp or xenon lamp, or a light source constituted by a light-emitting element such as light-emitting diodes (LEDs)) for illuminating a document placed on a platen glass and a first mirror are arranged, second and third mirrors, an imaging lens and an imaging element (for example, a line sensor such as a CCD (Charge Coupled Device)). Many of such image reading apparatuses are configured to read a document image by causing reflected light from the document illuminated by a light source portion to pass through a slit provided in a base such as a frame body of the illuminating device, and to travel via a first mirror, a second mirror, a third mirror and then an imaging lens to form an image on an imaging element.
For example, such image reading apparatuses are used as image reading means in the case where information of the image formed on the imaging element such as a CCD is converted to electric signals to be subjected to image processing, and the processed electric signals are transferred to an image forming apparatus that performs printing based on the image information, or in the case where the electric signals are sent to a computer (for example, personal computer) connected to a network.
Conventionally, an illuminating device provided in an image reading apparatus is known which includes a light source portion, an elongated and translucent light-guiding member that illuminates an illumination target from an elongated light emitting face extending along a longitudinal direction of the light-guiding member by guiding light from the light source portion, and a holding member that holds the light-guiding member.
Specifically, an illuminating device has been disclosed which includes a light-emitting body formed by arranging a plurality of light-emitting elements in a line, which reflects light from the light-emitting element with a reflecting member, and emits the reflected light toward the reading range of the document via the light-guiding member held by the holding member (for example, see FIGS. 7 to 10 and FIG. 13 of Patent Document 1 cited below).